RFC: fp printing speedup patch

[Paolo Carlini]

Paolo Carlini wrote:

> Therefore, after all, I don't think the various __*_to_char should be
> templates parameterized on _CharT, but simple functions working on
> chars, perhaps including the widen(c) loop at the end.

... well, of course if we want for the widen(c) loop to be *inside* the
various __*_to_char functions those must be template in order to pick
the right ctype<charT>::widen.

Probably it's cleaner to have the widen(c) loop part of _M_insert_int
and _M_indert_float.

Paolo.